A laboratory‐scale, batch‐type, in‐vessel composter was charged with simulated municipal solid waste deliberately contaminated with a mixture of 3‐ and 4‐ringed polycyclic aromatic hydrocarbons. The extent of their biodegradation was monitored over a 2‐month period (30 days of active composting and 30 days of compost curing) by use of soxhlet extraction and gas chromatography analysis. The results indicated that most of biodegradation occurred in the active composting phase and very little occurred during the curing phase of the composting process. Fluorene was too volatile for this type of bioremediation, and benz[a]anthracene was persistent in the compost throughout both phases of the experiment. Anthracene, phenanthrene, and pyrene showed excellent reduction in the actively composting phase, in contrast to their mercuric chloride–poisoned controls, indicating that biodegradation (not abiotic mechanisms) was the removal process from the composting mass.